The present invention relates to a process for the production of ethylenically unsaturated carboxylic acid esters, particularly α, ß unsaturated carboxylic acid esters, more particularly acrylic acid esters such as alkyl (alk)acrylates particularly alkyl (meth)acrylates such as methyl (meth)acrylates by the condensation of carboxylic acid esters with formaldehyde or a source thereof in the presence of bases, in particular, but not exclusively, a process for the production of alkyl esters of (meth)acrylic acid, for example, methyl methacrylate, by the condensation of propionic alkyl esters, for example methyl propionate, with formaldehyde or a source thereof in the presence of such a base. The invention is particularly relevant to the production of methyl methacrylate (MMA).
Such esters may be made by reacting an alkanoic ester of the formula R3—CH2—COOR4, where R3 and R4 are each, independently, a suitable substituent known in the art of acrylic compounds such as an alkyl group, especially a lower alkyl group containing, for example, 1-4 carbon atoms, with a suitable methylene source such as formaldehyde. Thus, for instance, alkyl esters of methacrylic acid, especially methyl methacrylate, may be made by the catalytic reaction of methyl propionate, with formaldehyde as a methylene source.
As mentioned above, a known production method for MMA is the catalytic conversion of methyl propionate (MEP) to MMA using formaldehyde. U.S. Pat. No. 6,544,924 describes the production of ethylenically unsaturated acid esters by the catalytic reaction of an alkanoic acid ester, especially methyl propionate, with formaldehyde in the presence of a silica supported catalyst. The production of methyl methacrylate (MMA) from methyl propionate, methanol and formalin using these catalysts was carried out at 350° C. and resulted in yields of MMA and MA between 3 and 12% and selectivities for MMA and MA between 88 and 97%.
It is known that the catalytic efficiency of a catalyst used for the production of an ethylenically unsaturated carboxylic acid ester may decrease over a period of time.
WO00/58298 describes a process for the production of α-methylenelactones and α-substituted hydrocarbylidenes by heating lactones and formaldehyde in the presence of a base. The base may be regenerated by contact with oxygen (O2) at elevated temperatures of up to 500° C. The use of high temperatures is disadvantageous economically.